Dry eye signs may signal risk for diabetic foot ulcers

Consider a patient’s case history when conducting assessments for potential diagnosis

I practice in a multidisciplinary setting where professional collaborative engagement of all medical specialties is highly valued and practiced on a daily basis.

I learned about a new test from podiatrists on staff in our health centers called the Semmes-Weinstein 5.07 (10-gram) monofilament test for loss of protective sensation of diabetic/neuropathic feet. 

The Semmes-Weinstein monofilament test (SWM) is a nylon filament calibrated so that it takes 10 grams of force to bend it when touched on the skin of the foot. An inability of the patient to detect this degree of force indicates that the client has a loss of protective sensation in the foot.

In 2008, a task force was built to consider the elements of a comprehensive foot and risk assessment of the patient with diabetes. 

The task force was comprised of the Foot Care Interest Group of the American Diabetes Association (ADA), with endorsement by the American Association of Clinical Endocrinologists (AACE).¹Previously by Dr. Mastrota: Explore the relationship between dry eye and sleep 

Foot exam considerations

The lifetime risk of a person with diabetes developing a foot ulcer may be as high as 25 percent, whereas the annual incidence of foot ulcers is < 2 percent.²

The most common triad of causes that interact and ultimately result in foot ulceration has been identified as neuropathy, foot deformity, and foot trauma.³

For the foot exam, case history is a pivotal component of risk assessment. A patient cannot be fully assessed for risk factors for foot ulceration based on history alone; a careful foot exam remains the key component of this process. 

Noteworthy aspects of the patient history include previous foot ulceration or amputation. Other important assessments in the history include neuropathic or peripheral vascular symptoms, impaired vision, or renal replacement therapy. 

Tobacco use should be recorded, as cigarette smoking is a risk factor not only for vascular disease but also for neuropathy.⁴

Eyecare providers know that beyond the associated retinal pathology, diabetes has been demonstrated to impact corneal nerve morphology and ocular surface integrity. 

diabetes is associated with progressive damage to corneal nerves and epithelial cells. Corneal nerve length and corneal nerve thickness changes are evident even in the early stages of diabetes mellitus (DM).⁵Related: How diabtes affects your patients 

Corneal neuropathy can lead to loss of corneal sensation and ultimately result in neurotrophic ulcers and significant visual morbidity. 

The epithelial fragility and poor wound healing that result from reduced epithelial adhesion to the underlying basement membrane in diabetes-together with corneal neuropathy-are thought to increase the susceptibility to dry eye disease (DED), persistent corneal erosions and infection, as well as to increase the risk of post-surgical complications.⁶

To parallel, loss of corneal sensation (corneal hypoesthesia) can be quantified by the use of the handheld Luneau Cochet-Bonnet Aesthesiometer. The device, akin to the monofilament foot test, contains a thin, retractable, nylon monofilament. Variable pressure can be applied to the cornea by the device-quantifying corneal sensation-by adjusting the length. The monofilament ranges from 60 mm to 5 mm. As the length is decreased, the pressure increases from 11 mm/gm to 200 mm/gm.

This begs the question:

As guardians of a patient’s wellbeing-and in the current outcomes-driven medical environment-should ODs have patients with dry eye take off their shoes and socks for the Semmes–Weinstein test? 

Read more by Dr. Mastrota 

References:

1. Bolton AJM, Armstrong DG, Albert SF, Frykberg RG, Hellman R, Kirkman SM, Lavery LA, LeMaster JW, Mills JL, Mueller MJ, Sheehan P, Wukich DK. Comprehensive foot examination and risk assessment: a report of the Task Force of the Foot Care Interest Group of the American Diabetes Association, with endorsement by the American Association of Clinical Endocrinologists. Diabetes Care. 2008 Aug; 31(8): 1679–1685.
2. Singh H, Armstrong DG, Lipsky BA. Preventing foot ulcers in patients with diabetes. JAMA. 2005 Jan 12;293(2):217-28.
3. Reiber GE, Vileikyte L, Boyko EJ, del Aguila M, Smith D, Lavery LA, Boulton AJ. Causal pathways for incident lower-extremity ulcers in patients with diabetes from two settings. Diabetes Care. 1999 Jan;22(1):157-62.
4. Clair C, Cohen MJ, Eichler F, Selby KJ, Rigotti NA. The effect of cigarette smoking on diabetic peripheral neuropathy: a systematic review and meta-analysis. J Gen Intern Med. 2015 Aug; 30(8): 1193–1203.
5. Reiber GE, Vileikyte L, Boyko EJ, del Aguila M, Smith DG, Lavery LA, Boulton AJ. Causal pathways for incident lower-extremity ulcers in patients with diabetes from two settings. Diabetes Care. 1999 Jan;22(1):157-62.
6. Markoulli M, Flanagan J, Tummanapalli SS, Wu J, Willcox M. The impact of diabetes on corneal nerve morphology and ocular surface integrity. Ocul Surf. 2018 Jan;16(1):45-57.